The USB Implementers Forum (USB-IF) has adopted Certified Wireless USB as the wireless extension to USB. Using the WiMedia ultra wideband (UWB) protocol, Certified Wireless USB provides the same bandwidth as wired Hi-Speed USB. This bandwidth represents almost 500 times the throughput of other wireless standards, such as Bluetooth. Certified Wireless USB aims to bring to wireless products the simplicity, functionality, and intuitive user experience of wired USB. Products based on Certified Wireless USB technology are beginning to enter the market even now.
Wired USB is an extremely successful standard; literally billions of USB peripherals are manufactured worldwide. Unfortunately, this translates into billions of tangled wires. With Wireless USB, users can download pictures from a camera without digging out the memory card, upload songs to an MP3 player without a proprietary cable, and place a large printer where it's convenient rather than close enough for its cable to reach the computer.
The USB-IF embraced Certified Wireless USB with backing from Intel, Microsoft, NEC, HP and other industry leaders. As an industry standard, devices based on the Certified Wireless USB technology from various vendors interoperate just as wired USB devices do now. The same host/peripheral usage model is retained. This means that there is one host, a PC, which connects to multiple peripherals. This standard differs from networking standards, where peers connect to other peers through one or more paths. This difference allows for USB's ease of use and its affordability.
The WiMedia Alliance UWB specification defines the radio protocol used by Wireless USB. UWB transmits on a large swath of frequencies simultaneously. Wireless USB uses the frequencies from 3.4 to 5.0 GHz (also known as band group one). Using such a large spectrum allows for high data rates and immunity from narrowband interference. The disadvantage is that UWB operates in licensed spectra. To avoid interfering with existing broadcasts, UWB power must be kept below noise level (and must adhere to other requirements). This noise level limitation restricts WiMedia UWB's range to approximately 10 meters. All UWB devices require certification and approval from the appropriate governmental agencies, including the Federal Communications Commission.
WiMedia UWB uses a distributed reservation protocol (DRP). In a local group, each WiMedia device reserves time slots. This method allows different protocols (e.g., Certified Wireless USB, WiNet, Bluetooth 3.0) to coexist while sharing the same underlying UWB spectrum—using it at different times. WiMedia devices transmit and listen for beacon frames to detect nearby devices and the time slots they use. The group's reservation is dynamically adjusted to avoid collisions—even as new devices and groups come in and out of range. The Certified Wireless USB specification allows peripherals to either self-beacon or manage beacons as directed by the Wireless USB host.
Certified Wireless USB creates a high bandwidth wireless network approximately 10 meters around a host PC. Devices actively seek out neighbors, manage flow control, and negotiate transmission time slots. Wireless traffic is encrypted (AES-128) to mimic the natural security of a wired connection. Like USB 2.0, wireless USB transfers data at up to 480 Mbps, retains the same host/peripheral model, and operates with the same drivers. This means new wireless peripherals can use the same host drivers as their wired USB versions. However, unlike wired USB, Certified Wireless USB devices require association.